Catadioptric reduction lens

ABSTRACT

A catadioptric projection lens configured for imaging a pattern arranged in an object plane ( 2 ) onto an image plane ( 4 ) while creating a single, real, intermediate image ( 3 ) has a catadioptric first section ( 5 ) having a concave mirror ( 6 ) and a beam-deflection device ( 7 ), and a dioptric second section ( 8 ) that commences after the beam-deflection device. The system is configured such that the intermediate image follows the first lens ( 17 ) of the dioptric section ( 8 ) and is preferably readily accessible. Arranging the intermediate image both between a pair of lenses ( 17, 21 ) of the dioptric section and at a large distance behind the final reflective surface of the beam-deflection device helps to avoid imaging aberrations.

The following disclosure is based on German Patent Application No.10127227.8 filed on May 22, 2001, which is incorporated into thisapplication by reference.

BACKGROUND OF THE INVENTION

1. Field of Invention

The invention relates to a catadioptric projection lens for imaging apattern arranged in an object plane onto an image plane.

2. Description of the Related Art

Projection lenses of said type are employed on projection illuminationsystems, in particular wafer scanners or wafer steppers, used forfabricating semiconductor devices and other types of micro-devices andserve to project patterns on photomasks or reticles, hereinafterreferred to generically as “masks” or “reticles,” onto an object havinga photosensitive coating with ultrahigh-resolution on a reduced scale.

In order to create even finer structures, it will be necessary to bothincrease the numerical aperture (NA) of the projection lens to beinvolved on its image side and to employ shorter wavelengths, preferablyultraviolet light with wavelengths less than about 260 nm.

However, there are very few materials, in particular, synthetic quartzglass and crystalline fluorides, such as calcium fluoride, magnesiumfluoride, barium fluoride, lithium fluoride, lithium calcium aluminumfluoride, lithium strontium aluminum fluoride, and similar, that aresufficiently transparent in that wavelength region available forfabricating the optical elements required. Since the Abbé numbers ofthose materials that are available lie rather close to one another, itis difficult to provide purely refractive systems that have beensufficiently well-corrected for chromatic aberrations. Although thisproblem could be solved by employing purely reflective systems,fabricating such mirror systems requires substantial expense and effort.

In view of the aforementioned problems, catadioptric systems thatcombine refracting and reflecting elements, i.e., in particular, lensesand mirrors, are primarily employed for configuring high-resolutionprojection lenses of the aforementioned type.

Whenever imaging reflective surfaces are employed, it will be necessaryto use beam-deflecting devices if images free of obscurations andvignetting are to be achieved. Both systems having one or moredeflecting mirrors and systems having solid beam-splitters are known.Additional plane mirrors may also be employed for folding the opticalpath. Folding mirrors are usually employed only in order to allowmeeting space requirements, in particular, in order to orient the objectand image planes parallel to one another. However, folding mirrors arenot absolutely necessary from the optical-design standpoint.

Employing systems having a solid beamsplitter in the form of, e.g., abeamsplitter cube (BSC), has the advantage that it allows implementingon-axis systems. Polarization-selective reflective surfaces that eitherreflect or transmit incident radiation, depending upon its predominantpolarization direction, are employed in such cases. The disadvantage ofemploying such systems is that hardly any suitable transparent materialsare available in the desired, large volumes. Moreover, fabricatingoptically active beamsplitter coatings situated within beamsplittercubes is extremely difficult. Heating effects occurring withinbeamsplitters may also present problems at high radiant intensities,since inside the beamsplitters an intermediate image is created.

One example of such a system is depicted in European Pat. No. EP-A-0 475020, which corresponds to U.S. Pat. No. 5,052,763, where the maskinvolved lies directly on a beamsplitter cube and the intermediate imageformed lies within the beam-splitter cube, behind its internalbeamsplitting surface. Another example is depicted in U.S. Pat. No.5,808, 805 and the associated application for continuation of same, U.S.Pat. No. 5,999,333, where a multi-element compound-lens group with apositive refractive power lies between the object plane and abeamsplitter cube. The collected light beam is initially deflectedtoward a concave mirror by the beamsplitter cube and then reflected backto the beamsplitter cube and through its beamsplitting surface towardthe aforementioned compound-lens group with a positive refractive powerby the concave mirror. The intermediate image lies within thebeamsplitter cube, in the immediate vicinity of its beamsplittingsurface. However, none of these documents makes any statements regardingheating problems that might arise or how they may be avoided.

European Patent No. EP-A-0 887 708 states measures for avoidingthermally induced imaging errors for a catadioptric system having abeamsplitter cube, but apparently no intermediate image falling withinits beamsplitter cube. The intention here was obtaining a symmetricdistribution of radiant intensity over the beam-splitter cube'sbeamsplitting surface, i.e., a distribution that would yield a heatingprofile symmetrically distributed over the beam-splitter's beamsplittingsurface, by suitably routing the beam transiting the beamsplitter cube.It was stated that the resultant wave-front distortions, such as thosethat result from nonuniform heating, which are difficult to eliminate,were avoidable.

Some of these disadvantages of systems having beamsplitter cubes may beavoided in the case of systems having one or more deflecting mirrors intheir beam-deflecting device. However, such systems have thedisadvantage that they are, by virtue of their design, necessarilyoff-axis systems.

A catadioptric reduction lens of that type is described in European Pat.No. EP-A-0 989 434, which corresponds to U.S. Ser. No. 09/364382. Thesetypes of lenses have a catadioptric first section having a concavemirror and a beam-deflection device that is followed by a dioptricsecond section arranged between their object plane and their imageplane. Their beam-deflecting device, which is configured in the form ofa reflecting prism, has a first reflective surface for deflectingradiation coming from their object plane to a concave mirror and asecond reflective surface for deflecting radiation reflected by thatconcave mirror to a second section containing exclusively refractiveelements. Their catadioptric first section creates a real intermediateimage that lies slightly behind this prism's second reflective surfaceand well ahead of the first lens of their second section. Theirintermediate image is thus readily accessible, which may be takenadvantage of for, e.g., installing a field stop.

Another reduction lens that has a beam-deflection device having adeflecting mirror is described in U.S. Pat. No. 5,969,882, whichcorresponds to European Pat. No. EP-A-0 869 383. This system'sdeflecting mirror is arranged such that light coming from its objectplane initially strikes the concave mirror of its first section, whereit is reflected to the system's beam-deflecting device's deflectingmirror, where it is reflected to a second reflective surface, where itis deflected toward the lens of the system's exclusively dioptric secondsection. The elements of this system's first section that are utilizedfor creating its intermediate image are configured such that itsintermediate image lies close to its beam-deflecting device's deflectingmirror. Its second section refocuses its intermediate image onto itsimage plane, which may be oriented parallel to its object plane, thanksto the reflecting surface that follows its intermediate image in theoptical train.

U.S. Pat. No. 6,157,498 depicts a similar configuration whoseintermediate image lies on, or near, the reflective surface of itsbeam-deflecting device. Several lenses of its second section arearranged between its beam-deflecting device and a deflecting mirrorlocated in its second section. In addition, an aspheric surface isarranged in the immediate vicinity of, or near to, its intermediateimage exclusively for the purpose of correcting for distortions, withoutaffecting other imaging errors.

A projection lens having a reducing catadioptric section and anintermediate image in the vicinity of the deflecting mirror of abeam-deflection device is depicted in German Pat. No. DE 197 26 058.

The U.S. patent mentioned above, U.S. Pat. No. 5,999,333, depictsanother catadioptric reduction lens having deflecting mirrors for whichlight coming from its object plane initially strikes a concave mirror,where it is reflected to the lens' beam-deflecting device's solereflective surface. The intermediate image created by its catadioptricsection lies close to this reflective surface, which reflects lightcoming from that concave mirror to a dioptric second section that imagesthis intermediate image onto its image plane. Both its catadioptricsection and its dioptric section create reduced images.

A similarly configured lens for which the intermediate image created byits catadioptric section lies near its deflecting device's solereflective surface is depicted in Japanese Pat. No. JP-A-10010429. Thesurface of the lens of the following dioptric section that lies closestto the deflecting mirror is aspheric in order that it may make aparticularly effective contribution to correcting for distortions.

Those systems whose intermediate image lies near, or on, a reflectivesurface may be compactly designed. They also allow keeping the fieldcurvatures of these systems, which are off-axis illuminated, that willneed to be corrected small. One of their disadvantages is that even theslightest flaws on any of their reflective surfaces may adversely affectthe qualities of images projected onto their image plane. Moreover,their focusing of radiant energy onto reflective surfaces may causeheating effects that might adversely affect their imaging performance.The resultant, locally high, radiant intensities may also damage thereflective coatings that are normally applied to the surfaces of mirrorblanks.

SUMMARY OF THE INVENTION

The problem addressed by the invention is avoiding the disadvantages ofthe state of the art. One particular object is to provide a projectionlens whose imaging performance will be relatively insensitive tofabrication tolerances.

As a solution to these and other objects, the invention, according toone formulation, provides a catadioptric projection lens for imaging apattern situated in an object plane of the projection lens onto an imageplane of the projection lens while creating a real intermediate image,which includes:

a catadioptric first section with a concave mirror and a beam-deflectingdevice located between said object plane and the image plane; and

a dioptric second section arranged following the beam-deflecting device;

wherein the second section starts after a final reflective surface ofthe catadioptric section and includes at least one lens arranged betweenthe final reflective surface and the intermediate image.

Beneficial embodiments thereon are stated in the dependent claims. Thewording appearing in all of the claims is herewith made a part of thecontents of this description.

A projection lens in the sense of the invention that is of the typementioned at the outset hereof is characterised in that its second,dioptric section, which starts behind the final reflective surface ofits beam-deflecting device, has at least one lens arranged between saidfinal reflective surface and its intermediate image. Said intermediateimage thus lies within its second, exclusively refractive, section inorder that at least one of the lenses of said second section thatprecede said intermediate image in the optical train may contribute tocreating said intermediate image. The invention thus foresees that thedistance between said final reflective surface of said beam-deflectingdevice and said intermediate image will be considerable, which mayallow, e.g., creating an accessible intermediate image in order to,e.g., allow installing a field stop in order to reduce stray-lightlevels. It will be particularly beneficial if that large distance willprovide that said final reflective surface lies in a zone where the beamdiameter is rather large, which will provide for its uniformillumination while avoiding hazardous, localized, peaks in radiantintensity and spread any heating of the optical element to which saidreflective surface has been applied over a larger area, which will, inturn, improve its imaging performance. More important, however, is thatany minor flaws that may be present on its reflective surface will haveonly a negligible, or no, effect on the qualities of images projectedonto the image plane. Lenses with high imaging performance may thus beconstructed, in spite of the minimal demands on the uniformity andfigure of said final reflective surface.

The term “final reflective surface,” as used here, is to be interpretedas referring to that reflective surface that lies immediately ahead ofsaid intermediate image in the optical train, where said surface may bea polarization-selective beamsplitting surface of a beamsplitter cube(BSC) or the surface of a highly reflective deflecting mirror, which maybe preceded by another deflecting mirror of a beam-deflecting device inthe optical train. Rear-surface mirrors in the form of deflecting prismsare also feasible. In the case of projection lenses according to theinvention, said “final reflective surface” concludes their catadioptricsection. Said final reflective surface may be followed by anotherreflective surface that causes a beneficial, from the structuralstandpoint, folding of said projection lens' optical path that has beenadded at the entrance to, or between the lenses of, said section inorder to, e.g., allow orienting said projection lens' object and imageplanes parallel to one another.

Said optical element between said final reflective surface and saidintermediate image that has been termed a “lens” here may also differfrom conventional lenses in form and function and may be in the form of,e.g., a planar plate having an aspheric correction, a truncated lens, ora half-lens. The term “lens,” as used here, thus, in general, refers toany transparent optical medium that optically affects transmittedradiation.

The aforementioned benefits apply regardless of whether a lens isarranged between said final reflective surface and said realintermediate image, largely due to the large distance between same. Saiddistance, which shall hereinafter also be referred to as the“intermediate-image distance,” should preferably be chosen such that thediameter of the beam at a surface orthogonal to said optical axis at theintersection of said final reflective surface with said optical axiswill be at least 10% of the diameter of said concave mirror, e.g., 17%or more of said diameter. However, said distance should not be so largethat said ratio of the diameter of said beam to the diameter of saidconcave mirror will be much greater than 20% or 25% in order to confinethe field curvatures that will need to be corrected to manageablelevels. Said large intermediate-image distance will allow arranging saidat least one lens between said final reflective surface and said realintermediate image, where said lens or lenses will preferably have apositive refractive power or powers, which will keep the diameter ofthose lenses that follow said intermediate image small, which, in turn,will allow designing said second section in manners that will allowreducing the quantities of materials required.

Arranging at least one lens between said final reflective surface andsaid real intermediate image also provides hitherto unknownopportunities for minimizing, or totally eliminating, the deleteriouseffects of lens heating. In order to reduce or preclude same, apreferred embodiment of the invention has a front intermediate-imagelens arranged on its object side, ahead of said intermediate image, anda rear intermediate-image lens arranged on its image side, behind saidintermediate image, where said intermediate-image lenses aresymmetrically arranged with respect to said intermediate image such thatany asymmetric contributions to imaging errors, such as coma, caused byheating of said intermediate-image lenses will be partially compensated,even nearly fully compensated, as shall be discussed in greater detailin terms of the sample embodiments to be discussed below.

The aforementioned symmetric arrangement of said front and rearintermediate-image lenses employed for partially or fully compensatingfor the effects of asymmetric heating of lenses situated in the vicinityof said intermediate image will be beneficial for both projection lensesof said type and other optical imaging systems that create at least onereal intermediate image.

Obtaining the favorable arrangement of said intermediate image accordingto the invention will be simplified if said first, catadioptric sectiondoes not contribute, or does not materially contribute, to the overallreduction ratio of said projection lens. Said catadioptric first sectionof said projection lens should preferably have a magnifications, β_(M),that exceed 0.95 and preferred embodiments of same will havemagnifications of β_(M)>1, i.e., will create enlarged intermediateimages, which will facilitate shifting same to said refractive secondsection.

In order to keep the field curvatures that will need to be correctedsmall in spite of said favorable arrangement of said intermediate image,it will be preferable to provide means for correcting for sphericalaberration produced by said first section, which, in turn, will providethat the axial locations of its paraxial intermediate image and theintermediate image created by outlying marginal rays will be shiftedsuch that they are closer proximity with respect to one another. It willbe beneficial if the longitudinal spherical aberration, SAL, produced bysaid first section satisfies the condition 0<|SAL/L|<0.025, where L isthe geometric distance between said object plane and the image plane ofsame, as shall be discussed in greater detail below.

Preferred embodiments of the invention will provide that that surface ofthat lens of said refractive section that lies closest to saidintermediate image will be spherical. However, the surfaces of bothlenses facing said intermediate image might also be spherical, whichwill allow fabricating lenses with high imaging performances and lowscatter in their imaging performances without need for imposingextremely stringent tolerances on same, since the figuring accuraciesattainable during fabrication are generally better for sphericalsurfaces than for aspherical surfaces, which also may exhibittransmittance gradients and excessive surface microroughnesses. On theother hand, those surfaces in the vicinity of intermediate images haveextremely strongly impacts on corrections for imaging errors, such asdistortion, which is why conventional lens designs frequently employaspherical surfaces near intermediate images. However, in the case ofthose projection lenses considered here, it will be preferable to employlenses with high-precision, nearly perfectly accurately figurable,spherical surfaces in the vicinity of said intermediate image.

The previous and other properties can be seen not only in the claims butalso in the description and the drawings, wherein the individualcharacteristics may be used either alone or in sub-combinations as anembodiment of the invention and in other areas and may individuallyrepresent advantageous and patentable embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal sectional drawing of a first embodiment of theinvention,

FIG. 2 is a longitudinal sectional drawing of a second embodiment of theinvention,

FIG. 3 is an enlarged view of the vicinity of the beam-deflection devicedepicted in FIG. 1,

FIG. 4 is a longitudinal sectional drawing of another embodiment of theinvention that has optical characteristics corresponding to those of theembodiment depicted in FIG. 1 and a folded second section, and

FIG. 5 is an embodiment of a microlithographic projection illuminationsystem according to the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following description of preferred embodiments of the invention,the term “optical axis” refers to a straight line or a sequence ofstraight-line segments passing through the centers of curvature of theoptical elements involved, where said optical axis will be folded at thereflective surfaces of deflecting mirrors or other reflective opticalelements. Directions and distances shall be designated as “image-side”directions or distances if they are directed toward either the imageplane involved or a substrate to be illuminated that is present in saidplane and as “object-side” directions or distances if they are directedalong that segment of said optical axis extending toward the objectinvolved. In the case of those examples presented here, said object maybe either a mask (reticle) bearing the pattern of an integrated circuitor some other pattern, such as a grating. In the case of those examplespresented here, the image of said object is projected onto a wafercoated with a layer of photoresist that serves as said substrate,although other types of substrate, such as components of liquid-crystaldisplays or substrates for optical gratings, may also be involved. Inthe following, identical or equivalent features of the variousembodiments of the invention will be assigned the same reference numbersfor greater clarity.

A typical design for a catadioptric reduction lens 1 based on a firstembodiment of same is depicted in FIG. 1 and serves to project a reducedimage, e.g., an image whose linear dimensions have been reduced by afactor of ¼, of a pattern on a reticle or similar that is arranged in anobject plane 2 onto an image plane 4 while creating a single, real,intermediate image 3. Said lens 1 has a catadioptric first section 5containing a concave mirror 6 and a beam-deflecting device 7 arrangedbetween its object plane 2 and image plane 3 and a dioptric secondsection 8 that contains exclusively refractive optical elementsfollowing said beam-deflecting device. Said beam-deflecting device 7 isconfigured in the form of a reflecting prism and has a first, planar,reflective surface 9 for deflecting radiation coming from said objectplane 2 toward said concave mirror and a second, planar, reflectivesurface 10 for deflecting radiation reflected by said imaging concavemirror 6 toward said second section 8. Said reflective surface 10represents both the final reflective surface of said catadioptricsection 5 and the final reflective surface of said beam-deflectingdevice 7. Although said first reflective surface 9 for deflectingradiation to said concave mirror 6 is necessary, said second reflectivesurface 10 may be deleted, in which case, said object plane and saidimage plane would be roughly orthogonal to one another if no otherdeflecting mirrors were employed. As may be seen from FIG. 4, theoptical train may also be folded within the bounds of said refractivesection.

As may be seen from FIG. 1, light from an illumination system (notshown) enters a projection lens from that side of said object plane 2opposite to said image plane and initially passes through a maskarranged in said object plane. Light transmitted by said mask thentransits a collecting lens 11 with a convex entrance surface, where saidcollecting lens is arranged between said object plane 2 and saidbeam-deflecting device 7, and then is deflected toward a mirror group 12that contains both said concave mirror 6 and a pair of negative lenses13, 14 situated immediately in front of same, each of which has itssurfaces curved towards the front surface of said concave mirror 6, bythe folding mirror 9 of said beam-deflecting device 7, where saidfolding mirror 9 is inclined at an angle with respect to the opticalaxis 15 of the preceding section differing from 45° that has been chosensuch that it deflects light incident on it through an angle greater than90°, e.g., through 100°. Light reflected by said concave mirror 6 thathas passed through said pair of negative lenses 13, 14 twice and beenreflected back to said beam-deflecting device 7 will be reflected towardsaid dioptric second section 8 by the second folding mirror 10 of saidbeam-deflecting device 7. The optical axis 16 of said second section isparallel to the optical axis 15 of said entrance section and thus allowsa mutually parallel orientation of said object plane 2 and said imageplane 3, which will simplify the operation of a scanner.

A special characteristic of said second section 8 is that said secondfolding mirror 10 is followed at a distance by a first lens 17, which,in the case of the example shown, is in the form of a biconcave positivelens whose positive refractive power contributes to the creation of saidreal intermediate image 3. In the case of the embodiment depicted, saidintermediate image will lie on the image side, following said first lens17 and at a distance from same, whereby a paraxial intermediate image,which has been indicated by a pseudoplane 18, lying closer to thespherical exit surface of said first lens 17 than the intermediate image19 created by outlying marginal rays.

A rear lens group 20 of said second section 8 that follows saidintermediate image 3 images said intermediate image 3 onto said imageplane 4. That lens 21 of said group 20 that lies closest to saidintermediate image 3 is in the form of a positive meniscus lens whosecurved surfaces are curved toward said object plane and whose distancefrom said intermediate image 3 exceeds the distance between saidintermediate image and said first lens 17 of said second section 8. Saidlens 21 is followed by another positive meniscus lens 22 whose curvedsurfaces are also curved toward said object plane and is arranged at alarge distance from same that, in turn, is followed by a curved meniscuslens 23 whose curved surfaces are curved toward said object plane, abiconcave negative lens 24, and a biconvex positive lens 25 arranged ataxial distances from same. Said lenses are followed by a negativemeniscus lens 26 whose curved surfaces are curved toward said objectplane and that has a slightly negative refractive power, which, in turn,is followed by a biconvex positive lens 27. A meniscus-shaped air space37 whose curved surfaces are curved toward said object plane is situatedbetween these latter lenses 26, 27. Another meniscus lens 28, which hasa positive refractive power and whose curved surfaces are also curvedtoward said object plane, that follows said lenses in the optical trainis immediately followed by a readily accessible system stop 29 arrangedsuch that said air space 37 in the vicinity of said stop 29 lies aheadof same in the optical train. Said stop 29 is followed by a negativemeniscus lens 30 whose concave surface faces said image plane that, inturn, is followed by a biconvex positive lens 31, a meniscus lens 32that has a positive refractive power and whose curved surface is curvedtoward said object plane, a thick, biconvex positive lens 33, andanother, small-diameter, biconvex, positive lens 34 that focus thetransmitted beam and direct it toward a wafer arranged in said imageplane 4. The optical element closest to said wafer is a plane-parallelend plate 35.

Table 1 summarizes the design specifications involved in tabular form,where the leftmost column thereof lists the number of the refractive,reflective, or otherwise designated surface, F, involved, the secondcolumn thereof lists the radius, r, of said surface [mm], the thirdcolumn thereof lists the distance, d, between the surface involved andthe next surface [mm], a parameter that is referred to therein as the“thickness”, and the fourth column thereof lists the refractive index ofthe material employed for fabricating the optical element following theentrance face, a parameter that is referred to therein as its “index.”The fifth column of said table is used for designating reflectivesurfaces, which are identified by the legend “REFL.” The overall length,L, of the lens involved, measured from its object plane to its imageplane, is about 1,250 mm.

In the case of this particular embodiment, eight of its surfaces areaspherical, namely the surface F7 and the surfaces F13, F20, F22, F29,F30, F36, F39, and F45.

In the figures, aspherical surfaces are hatched. Table 2 lists theassociated data for these aspherical surfaces, from which they may becomputed using the following equation:

p(h)=[((1/r)h ²)/(1+SQRT(1−(1+K)(1/r)² h ²)]+C1·h ⁴ −C2·h ⁶+. . . ,

where r is their local radius of curvature and h is the distance of apoint on their surface from their optical axis. p(h) thus represents theradial displacement of said point from the inflection point of thesurface in question along the z-direction, i.e., along their opticalaxis. The constants K, C1, C2, etc., are listed in Table 2.

The optical system 1 that may be reproduced using these data has beendesigned for use at a working wavelength of about 157 nm, at which thecalcium fluoride employed for fabricating all of the lenses involved hasa refractive index, n, of 1.55841. Its image-side numerical aperture,NA, is 0.80. Said system has been designed to have a field measuring 22mm×7 mm and is doubly telecentric.

The operation of said optical system and several of its beneficialfeatures will be described in greater detail below. The weakly positivefirst lens 11 of its catadioptric section 5 has a focal length that isroughly equal to the distance to same's concave mirror 6. Said concavemirror thus lies in the vicinity of a pupil of the system and may have arelatively small diameter, which will simplify its fabrication. Thefolding of the optical path at said section's first deflecting mirror 9through an angle exceeding 90° is beneficial in that it provides a largeworking distance over the lens' full width. The pair of negativemeniscus lenses 13, 14 immediately preceding said concave mirror 6correct for longitudinal chromatic aberration, CHL. In the case of thisparticular embodiment, it will be beneficial if only two lenses 13, 14are arranged within that portion of said catadioptric section 5 that istransited twice, since every lens situated within said portion has adouble effect on, e.g., transmittance and the wavefront distortions,without providing any additional leeway for correcting for same.

A feature that is particularly noteworthy is that said catadioptricsection 5, whose final optically effective surface is a deflectingmirror 10, either does not contribute to the system's overall reductionratio or makes only a minor contribution thereto. Said catadioptricsection has, in the embodiment shown here, a magnification, β_(M), givenby |β_(M)|=0.99, which makes a major contribution to the fact that thesystem's intermediate image 3 will be created at a great distance (theintermediate-image distance) down the optical train from said finaldeflecting mirror 10, which yields another benefit in that the radiantintensity incident on the second deflecting mirror 10 will be relativelyuniformly distributed over a larger area than that represented by thestate of the art, which, in turn, means that imaging errors due tononuniform heating in the vicinity of said deflecting mirror 10 or thesystem's beam-deflecting device 7 will either be reduced or avoidedaltogether. Said intermediate-image distance has been chosen here suchthat the diameter of the beam incident on a surface normal to theoptical axis 16 at the point where said second deflecting mirror 10intersects said optical axis will range from about 17% to about 18% ofthe diameter of said main concave mirror 6.

Since said intermediate image will not lie on, or in the immediatevicinity of, said deflecting mirror 10, minor errors in fabricating thereflective surface of said deflecting mirror 10 may be readilytolerated, since they will either not be imaged onto the system's imageplane 4 or will be defocused there and thus will have no adverse effectson images projected onto a wafer arranged on said image plane 4. Sincesaid final reflecting surface 10 is subjected to relatively uniformlydistributed radiant intensities only and minor errors in same aretolerable, it may be expected that the imaging performance of saidprojection lens 1 will remain unaffected by degradation of the (coated)surface of said mirror 10, even after many years of service incontinuous operation.

The axial distance between said final reflecting surface 10 of saidcatadioptric section 5 and said intermediate image 3 that follows samein the optical train will, in the case of the embodiment depicted, aswell as in all other embodiments of the invention, be so large that atleast one lens of the dioptric section 8 that follows said catadioptricsection in the optical train may be arranged between said finalreflecting surface 10 and said intermediate image 3. In the case of thesample embodiment depicted, said lens is a biconvex lens 17 whosepositive refractive power contributes to creation of said intermediateimage 3. Incorporating sufficiently high refractive power into theregion between said mirror 10 and said intermediate image will allowkeeping the diameters of those lenses that follow said intermediateimage 3 in the optical train small, which, in turn, will facilitatedesigning said dioptric section such that the quantities of materialsrequired for its fabrication will be reduced. One opportunity forrealizing said savings of materials will arise if said first lens 17 isfabricated in the form of a half-lens, which will be possible here,since only around half of its surface is optically utilized.

The invention allows optimizing catadioptric projection lenses having atleast one intermediate image in relation to the adverse effects ofasymmetric lens heating by adapting those lenses 17, 21 that surroundtheir intermediate image to suit one another in an appropriate, specialmanner. Said first lens 17 located on their object side, ahead of saidintermediate image 3, is also termed a “front intermediate-image lens,”while said meniscus lens 21 that follows said intermediate image is alsotermed a “rear intermediate-image lens.” Said intermediate-image lenses17, 21 should be symmetrically arranged with respect to saidintermediate image 3 such that contributions to imaging errors, such ascoma, due to heating of said lenses will be partially compensated orlargely fully compensated, where the first of said intermediate-imagelenses 17 may, so to speak, provide a preliminary grip on thermallyinduced imaging errors that will be compensated by the second of saidintermediate-image lenses 21 that follows it in the optical train, whichwill also be subject to heating. In the case of those off-axis systemsthat have been described here in terms of examples, those lensessituated in the vicinity of said intermediate image 3 will be extremelyasymmetrically illuminated, which will lead to same being subjected tohighly asymmetric heating effects. Said effects are largely responsiblefor uncorrectable distortions and coma occurring in images projectedonto wafers. However, it should be noted at this juncture that imagingerrors due to lens heating may limit imaging performance in the case ofthose catadioptric systems that have been described here in terms ofexamples.

If said lenses 17, 21 are symmetrically arranged about said intermediateimage 3 in the manner described above, then it may be arranged that,e.g., the height ratios, i.e., the distances from the optical axis 16,of the upper and lower marginal rays of the field beams at said frontand rear intermediate-image lenses 17, 21 will just barely reverse,which will allow using said rear intermediate-image lens 21 to partiallyor fully compensate for effects due to asymmetric heating of said frontintermediate-image lens 17.

The symmetry mentioned above in relation to compensating for asymmetriclens-heating effects will not usually be equivalent to any geometricsymmetries, e.g., symmetry with respect to reflection in the plane ofsaid intermediate image 3, which will be clear from the layout of theembodiment depicted in FIG. 1, for which the distance between itsintermediate image and the spherical exit surface of said frontintermediate-image lens 17 is less than the distance between same andthe aspherical entrance surface of said rear intermediate-image lens 21.

Among those lenses 17-35 situated within said second section 8, onlythose situated within its rearward lens group 20, i.e., all of saidlenses, with the lone exception of lens 17, contribute to imaging saidintermediate image onto the plane 4 of said wafer. Said lenses have beencombined in a manner suitable for correcting for imaging errors in saidintermediate image to the extent that a sufficient adequate correctionstatus will be obtained at the plane 4 of said wafer. Among those lensessituated within said rearward lens group 20, lens 21 closest to theintermediate image plays a special role in same, since any imagingerrors due to asymmetric heating of said lens will be at least partiallycompensated by said lens 17 situated ahead of said intermediate image,which provides a preliminary grip on thermally induced distortions,which will be eliminated upon transmission through said rearintermediate-image lens 21.

FIG. 2 depicts a sectional view of another embodiment whose detailedspecifications (data defining its aspherical surfaces) appear in Tables3 and 4. This particular reduction lens 1, which has also been designedfor a working wavelength of about 157 nm, has a basic layout similar tothat of the embodiment depicted in FIG. 1 and also has a numericalaperture, NA, of 0.80. The reference numbers employed here are identicalto those assigned to the corresponding lenses or lens groups appearingin FIG. 1. However, one major difference between this design and that ofFIG. 1 is that an intermediate group 41 of lenses comprising a biconvexpositive lens 42 facing its beamsplitter 7 and a biconcave negative lens43 facing a mirror group 12, has been arranged within that portion ofits optical train that is transited twice, roughly midway between saidbeamsplitter 7 and said mirror group 12. Increasing the refractive powerof said intermediate lens group 41 may beneficially affect the diameterof said mirror group 12, which may then be reduced. In addition to saidrear intermediate-image lens 21, a negative lens 44 has been arranged inthe vicinity of its intermediate image.

Unlike the embodiment depicted in FIG. 1, both the exit surface of saidfront intermediate-image lens 17 facing said intermediate image 3 andthe convex entrance surface of said rear intermediate-image lens 21facing said object plane are spherical, which will allow highlyaccurately figuring both of these surfaces situated near saidintermediate image, which, in turn, will allow minimizing imaging errorsdue to fabrication errors, such as surface irregularities or residualmicroroughness.

In the case of embodiments according to the invention, minorlongitudinal spherical aberration (SAL) at said intermediate image maybe beneficial. In the case of the typical overall length, L, of about1,250 mm involved here, SAL should not be more than about 30 mm, or atmost 20 mm, in order that the ratio SAL/L will not be much greater thanabout 0.025. Under such conditions, the field curvatures that will needto be corrected may be kept small, in spite of the largeintermediate-image distance involved, as will now be discussed ingreater detail based on FIG. 3, which schematically depicts the vicinityof the beamsplitter prism 7 depicted in FIG. 1, where said frontintermediate-image lens 17 has been schematically depicted only. Thesolid line designates a beam 45 close to the optical axis coming from aconcave mirror, where, in the case of low SAL, said beam will create amarginal-ray intermediate image 46 in the plane 18 of the paraxialintermediate image. Said beam is routed such that that marginal ray 47closest to said optical axis 16 will just barely fully strike the secondsurface 10 of said beamsplitter prism in order to provide imaging thatwill be free of vignetting. In the case of larger SAL, imaging that willbe free of vignetting will only be attainable under otherwise identicalconditions if the object field 48, and thus its associated intermediateimage 46′, shifts said beam further away from said optical axis 16, asindicated by the dotted line designating said shifted beam 45′, whosemarginal-ray intermediate image 46′ will be formed behind said plane 18of said paraxial intermediate image and at a certain distance from same.The location of said marginal ray 47 closest to said optical axis 16will remain virtually unaltered compared to the case of said beam 45,while the location of that marginal ray 49 farthest away from saidoptical axis will have moved further away from same, provided that thebeam divergence remains constant. It may be seen that the distancebetween said intermediate image 46 and said optical axis 16, i.e., thedistance between the plane 18 of said paraxial intermediate image andsaid marginal-ray intermediate image 46, will be reduced in step withreductions in SAL. Similar will apply to the location of the objectfield, which is why low spherical aberrations help keep the fieldcurvatures that will need to be corrected small.

Numerous variations on the invention, none of which have beenillustrated here, are feasible. For example, said folding mirrors 9, 10of said beam-deflecting device 7 may be replaced by separate foldingmirrors having another orientation, if necessary. In the case of lenseswith low numerical apertures and/or lenses with a side arm housing theirmain mirror 6 that is roughly normal to the structure housing theremainder of their optical elements, high-reflectance surfaces on theinner surfaces of, e.g., a deflecting prism, may be employed instead ofmirrors with reflective coatings. Said beam-deflecting device 7 equippedwith a pair of high-reflectance deflecting mirrors 9, 10 may also bereplaced by a solid beamsplitter, such as a beamsplitter cube having asingle beamsplitting surface that partially reflects and partiallytransmits incident radiation. Same might also be replaced by a partiallytransmitting mirror, although a polarization beamsplitter would bepreferable. The reflective surface involved would represent the finalreflective surface ahead of said intermediate image.

Another opportunity for configuring a projection lens according to theinvention is depicted in FIG. 4. Although the basic layout, i.e., thetypes of lenses involved, their numbers, their radii of curvature, theair spaces involved, etc., of the projection lens 1 depicted therein isidentical to that of the embodiment depicted in FIG. 1 (cf. Tables 1 and2), the beam-deflecting device 7, which is needed due to the type oflayout involved, employed here has just a single, planar deflectingmirror 9. A second deflecting mirror 10 has been arranged between therelatively widely spaced lenses 21, 22 within its second, dioptricsection 8, behind its intermediate image 3 in the optical train, inorder to obtain a parallel orientation of the plane 2 of said reticleand the plane 4 of said wafer for this type of layout as well. Sincesaid deflecting mirror 10 has been arranged behind said intermediateimage 3, it does not form part of said beam-deflecting device 7, whosefinal reflective surface will now be said deflecting mirror 9. In thecase of this type of design, light coming from said object plane 2initially strikes an imaging concave mirror 6 that reflects it towardsaid sole deflecting mirror 9 of said beam-deflection device 7. Theconvergent beam incident on said final deflecting mirror 9 is deflectedto said second, dioptric section 8, which is bent at a right angle dueto its integral deflecting mirror 10. A lens 17 of said second sectionis arranged between said deflecting mirror 9 and said intermediate image3, which is situated far from said deflecting mirror, exactly as in thecase of the other embodiments. All of the benefits of the embodimentdepicted in FIG. 1 are retained.

In the case of those embodiments described here, all of theirtransparent optical components are fabricated from the same material,namely, calcium fluoride. However, other materials, in particular, thosecrystalline fluoride materials mentioned at the outset hereof, that aretransparent at the working wavelength to be involved may also beemployed. At least one other material may also be employed in order to,e.g., correct for chromatic aberration, if necessary. The benefits ofthe invention may, of course, also be applied to systems intended foruse at other working wavelengths, e.g., 248 nm or 193 nm, falling withinthe ultraviolet spectral region. Since, in the case of those embodimentsdepicted here, a single material is employed for fabricating all oftheir lenses, adapting the designs that have been illustrated to use atother wavelengths will be a simple matter for optical specialists. Otherlens materials, such as synthetic quartz glass may be employed forfabricating some or all of their optical elements, particularly in thecase of systems intended for use at longer wavelengths.

Projection lenses according to the invention may be employed on anysuitable microlithographic projection illumination system, e.g., onwafer steppers or wafer scanners. FIG. 4 schematically depicts a waferscanner 50 comprising a laser light source 51 equipped with anassociated device 52 for narrowing its band width. An illuminationsystem 53 generates a large, sharply defined, highly uniformlyilluminated, image field that has been adapted to suit thetelecentricity requirements of the projection lens 1 that follows it inthe optical train. Said illumination system 53 is equipped with devicesfor selecting an illumination mode and may be switched between, e.g.,conventional illumination with a high degree of coherence, annularillumination, and dipole or quadrupole illumination. Said illuminationsystem is followed by a device 54 for holding and manipulating a mask 55such that said mask 55 lies in said object plane 2 of said projectionlens 1 and may be translated over said plane when said system isoperated in scanner mode. In the case of the wafer scanner depictedhere, said device 54 thus incorporates the scanner drive for said mask.

Said plane 2 of said mask is followed by said projection lens 1 thatprojects a reduced image of said mask onto a wafer 56 coated with alayer of photoresist that has been arranged in the image plane 4 of saidprojection lens 1. Said wafer 56 is held in place by a device 57 thatincludes a scanner drive in order to allow translating said wafer insynchronism with said mask. All of said systems are controlled by acontroller 58. The designs of such systems are known and will thus notbe discussed any further here.

The above description of the preferred embodiments has been given by wayof example. From the disclosure given, those skilled in the art will notonly understand the present invention and its attendant advantages, butwill also find apparent various changes and modifications to thestructures and methods disclosed. It is sought, therefore, to cover allchanges and modifications as fall within the spirit and scope of theinvention, as defined by the appended claims, and equivalents thereof.

TABLE 1 Surface No. Radius Thickness Index Reflective 0 0.0000 36.000 11 0.0000 0.000 1 2 303.9247 22.169 1.55841 3 2732.7256 96.271 1 4 0.00000.000 −1 REFL 5 0.0000 −468.173 −1 6 199.7080 −10.268 −1.55841 7485.9116 −25.206 −1 8 186.8130 −10.064 −1.55841 9 448.8758 −19.609 −1 10243.7460 19.609 1 REFL 11 448.8758 10.064 1.55841 12 186.8130 25.206 113 485.9116 10.268 1.55841 14 199.7080 469.450 1 15 0.0000 0.000 −1 REFL16 0.0000 −100.166 −1 17 −532.8260 −25.379 −1.55841 18 635.9179 −10.000−1 19 0.0000 −115.933 −1 20 −311.6936 −24.721 −1.55841 21 −729.4902−219.394 −1 22 −276.2460 −15.427 −1.55841 23 −448.8506 −75.934 −1 24−158.3810 −30.587 −1.55841 25 −163.4782 −40.576 −1 26 419.7809 −20.540−1.55841 27 −237.0092 −32.234 −1 28 −428.0516 −30.182 −1.55841 29693.3900 −23.874 −1 30 −241.2068 −10.000 −1.55841 31 −182.4638 −25.712−1 32 −422.9386 −36.706 −1.55841 33 327.0334 −7.823 −1 34 −150.5655−28.311 −1.55841 35 −314.2186 −15.947 −1 36 0.0000 −3.484 −1 37−172.8501 −12.272 −1.55841 38 −116.0764 −25.993 −1 39 −230.6308 −32.436−1.55841 40 465.5346 −4.280 −1 41 −153.0332 −30.802 −1.55841 42−514.5406 −8.487 −1 43 −157.6109 −41.061 −1.55841 44 2904.8207 −4.477 −145 −226.8988 −24.123 −1.55841 46 847.7062 −0.972 −1 47 0.0000 −10.000−1.55841 48 0.0000 −8.006 −1 49 0.0000 0.000 −1

TABLE 2 Surface No. K C1 C2 C3 C4 C5 C6  7 0 3.8786E−09 −1.5770E−131.6270E−17 −1.1233E−21 −1.5136E−26 8.5713E−31 13 0 3.8786E−09−1.5770E−13 1.6270E−17 −1.1233E−21 −1.5136E−26 8.5713E−31 20 03.6292E−09 6.7560E−14 5.6841E−19 −6.7883E−23 6.7834E−27 −2.0530E−31 22 01.1976E−08 7.3544E−14 7.0329E−19 −1.2632E−23 −3.0105E−27 2.0874E−31 29 0−8.3929E−09 −3.3961E−13 8.7632E−18 −1.4358E−21 5.5923E−26 2.0181E−30 300 1.7409E−08 −1.6961E−13 1.1828E−17 −3.0819E−21 1.7008E−25 −1.6848E−3035 0 −2.1445E−08 6.7395E−13 −4.8468E−17 5.9926E−21 −2.8763E−253.9059E−31 39 0 1.6042E−08 4.7884E−15 2.0832E−16 −2.8771E−20 1.7749E−24−1.9350E−29 45 0 −6.5639E−08 −8.2521E−12 −1.2733E−16 −1.1662E−20−1.5813E−23 6.3953E−27

TABLE 3 Surface No. Radius Thickness Index Reflective 0 0.0000 36.00001.000000 1 0.0000 0.0000 1.000000 2 333.2125 20.7650 1.558410 33917.6389 94.1110 1.000000 4 0.0000 0.0000 −1.000000 REFL 5 0.0000−148.1340 −1.000000 6 −595.2534 −32.1340 −1.558410 7 331.1147 −5.4880−1.000000 8 312.7988 −10.0000 −1.558410 9 −682.8537 −300.0000 −1.00000010 264.3436 −10.2440 −1.558410 11 731.0776 −28.2930 −1.000000 12191.6338 −10.0480 −1.558410 13 479.5908 −19.2310 −1.000000 14 254.969219.2310 1.000000 REFL 15 479.5908 10.0480 1.558410 16 191.6338 28.29301.000000 17 731.0776 10.2440 1.558410 18 264.3436 300.0000 1.000000 19−682.8537 10.0000 1.558410 20 312.7988 5.4880 1.000000 21 331.114732.1340 1.558410 22 −595.2534 146.3160 1.000000 23 0.0000 0.0000−1.000000 REFL 24 0.0000 −112.8570 −1.000000 25 −660.9668 −23.0610−1.558410 26 556.1870 −10.0000 −1.000000 27 0.0000 −116.4030 −1.00000028 −226.5082 −31.7500 −1.558410 29 −3414.2334 −25.1180 −1.000000 30−3354.8183 −10.0000 −1.558410 31 −314.6991 −217.5910 −1.000000 32−233.5958 −36.8330 −1.558410 33 960.2043 −32.3470 −1.000000 34 5805.6084−10.0020 −1.558410 35 −240.7709 −42.3390 −1.000000 36 169.2097 −20.9060−1.558410 37 −286.7201 −11.5480 −1.000000 38 −478.5727 −34.5630−1.558410 39 301.8036 −1.0000 −1.000000 40 −355.1135 −27.7490 −1.55841041 1378.0763 −56.2110 −1.000000 42 −415.3177 −10.0000 −1.558410 43−256.9507 −15.2090 −1.000000 44 −559.7690 −26.8590 −1.558410 45 479.6752−10.5000 −1.000000 46 0.0000 9.4930 −1.000000 47 −174.1879 −35.5680−1.558410 48 −7171.0639 −32.6510 −1.000000 49 183.6755 −13.5520−1.558410 50 255.5654 −2.3140 −1.000000 51 −242.4305 −34.8290 −1.55841052 9821.8721 −1.4240 −1.000000 53 −157.8195 −22.5240 −1.558410 54−257.8030 −1.1080 −1.000000 55 −125.4426 −52.2320 −1.558410 56 −545.5697−1.2640 −1.000000 57 −182.4345 −19.6850 −1.558410 58 3491.0716 −1.1000−1.000000 59 0.0000 −10.0000 −1.558410 60 0.0000 −8.0420 −1.000000 610.0000 0.0000 −1.000000

TABLE 4 Surface No. K C1 C2 C3 C4 C5 C6 11 0 6.1332E−09 −6.4063E−14−4.5499E−18 −2.3621E−22 2.4653E−26 −3.8399E−30 17 0 6.1332E−09−6.4063E−14 −4.5499E−18 −2.3621E−22 2.4653E−26 −3.8399E−30 29 03.5716E−09 −2.9481E−13 5.3916E−18 4.4070E−23 5.4581E−27 −7.3136E−31 31 0−1.8810E−08 2.0385E−13 −1.4483E−18 −5.4964E−22 1.5447E−26 1.0845E−30 350 −1.6228E−08 −2.1449E−13 −2.4296E−17 4.2715E−21 −5.4242E−25 3.1678E−2942 0 1.7399E−08 −7.3701E−13 −3.4088E−17 1.1643E−21 −4.5566E−261.2003E−30 47 0 3.9491E−09 −5.1757E−14 −4.2800E−18 6.4019E−22−1.0309E−25 −7.9826E−30 52 0 −1.7053E−08 8.0221E−13 −8.4651E−177.3497E−21 −5.0447E−25 9.0347E−30 57 0 1.3027E−07 4.8555E−12 −2.2801E−153.5482E−19 −5.9522E−23 1.5762E−26

What is claimed is:
 1. A catadioptric projection lens for imaging apattern situated in an object plane of the projection lens onto an imageplane of the projection lens while creating a real intermediate image,comprising: a catadioptric first section with a concave mirror and abeam-deflecting device located between said object plane and said imageplane; and a dioptric second section arranged following saidbeam-deflecting device; said second section starting after a finalreflective surface of said catadioptric section and comprising at leastone lens arranged between said final reflective surface and saidintermediate image; and said beam-deflecting device being a geometricbeam splitter having at least one planar reflective surface.
 2. Aprojection lens according to claim 1, wherein said intermediate image issituated in an empty space at a distance from an optical componentnearest said intermediate image.
 3. A projection lens according to claim1, wherein said intermediate image is freely accessible.
 4. A projectionlens according to claim 1, wherein said intermediate image is situatedat a distance from a final reflective surface of said beam-deflectingdevice, where said distance is chosen such that the diameter of raysincident on a surface orthogonal to the optical axis at an intersectionof said final reflective surface with said optical axis is at least 10%of the diameter of said concave mirror.
 5. A projection lens accordingto claim 1, wherein positive refractive power is arranged between saidfinal reflective surface and said intermediate image.
 6. A projectionlens according to claim 1, wherein a front lens is inserted on theobject side ahead of said intermediate image and a rear lens is insertedon the image side following said intermediate image and wherein thefront lens and the rear lens are roughly symmetrically arranged withrespect to said intermediate image such that asymmetric contributions toimaging aberrations by the front lens and the rear lens due to heatingof the front lens and the rear lens are at least partly compensated. 7.A projection lens according to claim 1, wherein there is provided atleast one lens of said second section having a surface facing saidintermediate image, the surface being spherical.
 8. A projection lensaccording to claim 6, wherein surfaces of the front lens and the rearlens facing said intermediate image are spherical.
 9. A projection lensaccording to claim 1, wherein said catadioptric first section has amagnification β_(M) greater than 0.95.
 10. A projection lens accordingto according to claim 1, wherein said catadioptric first section iscorrected for spherical aberration such that the longitudinal sphericalaberration, SAL, of said catadioptric first section satisfies thefollowing condition: 0<|SAL/L|<0.025, where L is the geometric distancebetween said object plane and said image plane.
 11. A projection lensaccording to claim 1, wherein an intermediate-lens group with at leastone lens is arranged in said catadioptric first section between thebeam-deflecting device and a mirror group, the mirror group includingsaid concave mirror and at least one negative lens.
 12. A projectionlens according to claim 11, wherein said intermediate-lens groupincludes at least one positive lens.
 13. A projection lens according toclaim 1, wherein said beam-deflecting device has a first mirroredsurface for deflecting radiation coming from said object plane to saidconcave mirror and a second mirrored surface, inclined at an angle withrespect to said first mirrored surface, for deflecting radiation comingfrom said concave mirror to said second section.
 14. A projection lensaccording to claim 1, wherein said beam-deflecting device has only asingle mirrored surface arranged such that it reflects radiation comingfrom the concave mirror to said second section.
 15. A projection lensaccording to claim 1, wherein a polarization-selective mirrored surfaceis arranged inside a beamsplitter cube.
 16. A projection lens accordingto claim 1, wherein a lens with a positive refractive power is arrangedbetween said object plane and said beam-deflecting device.
 17. Aprojection lens according to claim 1, wherein a system stop is providedand wherein a curved, meniscus-shaped, air space is situated ahead ofthe system stop and close to the same.
 18. A projection lens accordingto claim 1, wherein at least the image side is telecentrically designed.19. A projection lens according claim 1, wherein it is designed for usewith ultraviolet light falling within the wavelength range extendingfrom 120 nm to approximately 260 nm.
 20. A projection illuminationsystem for use in microlithography including an illumination system anda catadioptric projection lens for imaging a pattern situated in anobject plane of the projection lens onto an image plane of theprojection lens while creating a real intermediate image, thecatadioptric projection lens comprising: a catadioptric first sectionwith a concave mirror and a beam-deflecting device located between saidobject plane and said image plane; and a dioptric second sectionarranged following said beam-deflecting device; wherein said secondsection is located after a final reflective surface of said catadioptricsection and comprises at least one lens arranged between said finalreflective surface and said intermediate image; and wherein saidbeam-deflecting device is a geometric beam splitter having at least oneplanar reflective surface.
 21. A method for fabricating semiconductordevices, or other types of microdevices, comprising: providing a maskhaving a prescribed pattern, illuminating said mask with ultravioletlight having a prescribed wavelength, and projecting an image of saidpattern onto a photosensitive substrate situated in the vicinity of theimage plane of a projection lens using a catadioptric projection lenshaving a catadioptric projection lens for imaging a pattern situated inan object plane of the projection lens onto an image plane of theprojection lens while creating a real intermediate image, the projectionlens including: a catadioptric first section with a concave mirror and abeam-deflecting device located between said object plane and said imageplane; and a dioptric second section arranged following saidbeam-deflecting device; said second section starting after a finalreflective surface of said catadioptric section and having at least onelens arranged between said final reflective surface and saidintermediate image; and said beam-deflecting device being a geometricbeam splitter having at least one planar reflective surface.
 22. Aprojection lens according to claim 1, wherein said catadioptric firstsection has a magnification β_(M) greater than unity.
 23. A catadioptricprojection lens for imaging a pattern situated in an object plane of theprojection lens onto an image plane of the projection lens whilecreating a real intermediate image, comprising: a catadioptric firstsection with a concave mirror and a beam-deflecting device locatedbetween said object plane and said image plane; and a dioptric secondsection arranged following said beam-deflecting device; said secondsection starting after a final reflective surface of said catadioptricsection and comprising at least one lens arranged between said finalreflective surface and said intermediate image; and said beam-deflectingdevice having a first reflective surface for deflecting radiation comingfrom said object plane to said concave mirror and a second reflectivesurface, inclined at an angle with respect to said first reflectivesurface, for deflecting radiation coming from said concave mirror tosaid second section.
 24. A catadioptric projection lens for imaging apattern situated in an object plane of the projection lens onto an imageplane of the projection lens while creating a real intermediate image,comprising: a catadioptric first section with a concave mirror and abeam-deflecting device located between said object plane and said imageplane; and a dioptric second section arranged following saidbeam-deflecting device; said second section starting after a finalreflective surface of said catadioptric section and comprising at leastone lens arranged between said final reflective surface and saidintermediate image; and said beam-deflecting device having only a singleplanar reflective surface arranged such that it reflects radiationcoming from the concave mirror to said second section.